Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$223.73	8.225%	$242.1318	$242.13	$242.15	$242.10
Purchase #2	$72.35	12.507%	$81.3988	$81.40	$81.40	$81.40
Purchase #3	$151.28	3.492%	$156.5627	$156.56	$156.55	$156.60
Purchase #4	$44.65	8.630%	$48.5033	$48.50	$48.50	$48.50
Purchase #5	$127.90	11.525%	$142.6405	$142.64	$142.65	$142.60
Purchase #6	$101.47	10.829%	$112.4582	$112.46	$112.45	$112.50
Purchase #7	$240.40	12.273%	$269.9043	$269.90	$269.90	$269.90
7 purchase totals =	$961.78		$1,053.5996	$1,053.59	$1,053.60	$1,053.60